1. Field of the Invention This invention relates to a street sweeper machine with trash pick-up and transport capabilities.
2. The Prior Art
As is known, some street sweeper machines designed for large surface sweeping, such as urban surfaces, are configured with a driver's cab, a tank containing water to be delivered to a surface being swept to damp it preparatory to sweeping proper so as to keep down dust, a bin for collecting trash picked up from the ground, brushes in contact with the ground surface, and a trash conveyor operative to receive trash from the brushes and discharge them into the trash bin. The brushes usually include both side and front brushes of frustrum or cup-like shape which are laid with their axis of rotation transverse to a surface to be swept, and a cylindrical or roll brush having its axis of rotation substantially parallel to said surface in a substantially center area of the machine.
The side and front brushes direct trash to the roll brush, and the latter redirects it to said trash conveyor.
The Applicant has made machines of the aforesaid type wherein the trash conveyor is located between the trash bin and the driver's cab, and extends vertically upwards from an area close to the ground surface in order to pick up trash more effectively, thereby the machine is split into two discrete regions: a forward region comprising the driver's cab, the engine, and steering front drive wheels, and a rearward region mostly engaged by the trash bin.
The trash conveyor is formed with plural moving paddles carried on chains and driven thereby, the chains being driven by sprocket wheels which are in turn driven by a specially provided motor.
The machines of the type just described have shown their operability and are quite compact in size for a given load capacity and throughput.
It has been found, however, in actual use that it is sometimes desirable to to increase the machine load capacity and dimensions, and more generally its overall performance.
This because dumping sites and trash incinerators tend to be established at increasingly longer distances from cities, on account of the growing concern for the pollution problems brought about of necessity by dumping sites and incinerators. Likewise, trash conversion plants for reclaiming power or any reusable substances contained therein tend to be established further away from dwelling areas.
As a result, the trash bin should be of sufficient capacity to not only provide for continued operation for many hours a day, but also so that frequent round trips to dumping sites or trash incinerator plants are not required.
Ideally, such a machine should be able to operate for a whole day to pick up trash and only reach the dumping site or incinerator, which may be several kilometers away, at the end of the daily work cycle.
Actual tests carried out by the Applicant have shown that machines of the type as aforesaid cannot be provided by merely enlarging prior machines or their trash bins.
In particular street sweeper machines, in order to carry out with adequate accuracy the basic trash picking up operations, are in the first place required to reach quickly and accurately all the areas to be swept clean, while avoiding the many obstructions encountered. Large size machines cannot move with sufficient nimbleness among the obstructions presented by cities unless a large steering angle is provided for their steering wheels. However, this appears to be irreconcilable with the sweeping operation: with a large steering angle, the paths travelled by the front and side brushes which direct the trash material leave over the ground path marks which do not overlap the path of the substantially centrally located cylindrical or roll brush.
It follows that not only are unswept areas left over the ground but also areas with dust and trash build-ups, that is with trash gathered by the side and front brushes which the roll brush has failed to pick up.
Further, if the steering angle of the wheels is increased, the roll brush, which has its axis of rotation substantially parallel to the ground and perpendicular to the main longitudinal dimension of the machine, may be dragged along paths which involve increased cross skidding thereof over the ground, that is paths having a large component parallel to the axis of the roll brush.
Such skidding movements tend to cause the bristles comprising the roll brush to be flexed towards the axis. It follows that, in tight cornering, the roll brush becomes distorted and flattens along the axis direction, thereby no longer being able to perform correctly its basic function of ground sweeping and above all of directing the trash material to the vertical conveyor. It may be also appreciated that such distortion of the roll brush brings about increased wear of the same and the need for replacement at frequent intervals.
With large size machines, maneuverability is also affected by lack of direct visibility by the driver of the areas being worked upon. The use of a variety of viewing mirrors can only partly remedy this problem.
It should be also noted that if the engine of prior machines is rated higher to afford adequate speed during the trips to dumping sites or incinerators, the net result is again an inadequate piece of machinery with poor street maneuverability.
In fact, in order to carry out the various street sweeping operations, powerplants are required which can operate for long periods at very low speeds, and which can operate at such very low speeds smoothly with no jerky response to controls so that all the movements can be controlled in an easy and accurate manner.
By enlarging prior machines and increasing their power, additional drawbacks are introduced, such as a higher vertical reach of the conveyor where the trash bin is made exceedingly large. This in order to ensure adequate filling of the bin, even when the latter has been filled almost to the brim.
It follows that the chains holding the trash conveyor paddles, which are to nearly span the full height of the bin from an area proximate the ground surface and which are subjected to significant stresses, cannot always be tensioned as is desirable. Slack tensioning results in reduced effectiveness of the conveyor.
Owing to such drawbacks, street sweeping machines of the above-mentioned type are currently made in relatively small sizes and cannot meet the above-noted work demands without involving significant breaks lasting upward of several hours for transporting the picked up trash a long distance at the end of the working cycle.